QC 

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A3 


LIBRARY 

OF  THE 

UNIVERSITY  OF  CALIFORNIA. 


GIFT    OF 


Class 


8061  'IZ  -N»f 

'AN  -  ' 

saaxvw 


U.    S.   DEPARTMENT   OF   AGRICULTURE. 

WEATHER    BUREAU. 


SOME  CLIMATIC  FEATURES  OF  THE 
ARID  REGIONS. 


COMMUNICATED   TO    THE 


NATIONAL   IRRIGATION    CONGRESS. 


AT   ITS 


FIFTH  ANNUAL  SESSION, 


PHCENIX,  ARIZONA,   DECEMBER  15-17,  1896, 


BY 


L..     MOORE, 

CHIEF  OP  WEATHER  BUREAU. 


WASHINGTON : 

WEATHER  BUREAU. 
1896. 


U.   S.   DEPARTMENT   OF   AGRICULTURE, 

WEATHER   BUREAU. 


SOME  CLIMATIC  FEATURES  OF  THE 
ARID  REGIONS. 


COMMUNICATED  TO   THE 


NATIONAL  IRRIGATION    CONGRESS. 


AT    ITS 


FIFTH  ANNUAL  SESSION, 

PHCENIX,  ARIZONA,  DECEMBER  15-17,  1896, 


BY 

L.    MOORE, 

CHIEF  OF  WEATHER  BUREAU, 

-odf 


WASHINGTON : 

WEATHER    BUREAU. 
1896. 


U.  S.  DEPARTMENT  OF  AGRICULTURE, 

WE!THER  BUREAU, 
Washington,  D.  C.,  December  1,  1896. 

To  THE  NATIONAL  IRRIGATION  CONGRESS, 

Phoenix,  Ariz. 

Mr.  President  and  Representatives: 

Finding  it  impossible  to  accept  your  invitation  to  deliver  an  ad- 
dress before  your  honorable  body  on  the  17th  instant,  on  the  subject 
of  ':  Sensible  Temperatures,"  I  herewith  transmit  for  your  considera- 
tion a  paper  having  for  its  purpose  the  presentation  of  a  few  salient 
features  of  climate  in  their  bearing  upon  the  irrigation,  sensible  tem- 
perature, and  kindred  physical  features  of  the  arid  and  subarid  re- 
gions of  the  great  West. 

In  the  preparation  of  the  charts,  and  in  collating  much  of  the  in- 
formation contained  in  the  text  of  this  paper,  I  have  pleasure  in 
acknowledging  the  valuable  assistance  rendered  by  Mr.  Alfred  J. 
Henry,  Chief  of  the  Division  of  Records  and  Meteorological  Data  of 
the  Weather  Bureau. 

Although  having  served  as  a  member  of  the  Government  Depart- 
mental Board  on  Irrigation  during  the  past  year,  I  feel  that  my 
knowledge  of  the  practical  application  of  irrigation  to  agriculture  is 
too  limited  to  justify  me  in  intruding  my  opinions  upon  the  many 
here  assembled  who  are  so  much  better  fitted  by  experience  and  edu- 
cation to  consider  the  problem,  still  I  desire  to  express  my  sympathy 
for,  and  hearty  interest  in,  your  noble  efforts  to  claim  for  the  present 
generation  fruitful  dominion  over  many  of  the  alluvial  valleys  and 
plains  now  unknown  to  the  plow  and  the.  reaper,  and  to  transmit  to 
posterity  an  empire  of  fertile  fields  and  thrifty  homes. 

Under  the  direction  of  the  Honorable  Secretary  of  Agriculture  it 
was  my  pleasure  on  September  20,  1895,  a  few  weeks  after  coming  to 
the  head  of  the  Weather  Bureau,  to  issue  instructions  to  the  observers 
of  the  weather  service  to  begin  the  telegraphing  from  observation 
stations  of  the  readings  of  the  wet-bulb  thermometer,  more  popularly 
known  as  the  "  sensible  "  temperature.  This  is  about  the  temperature 
felt  by  animal  life  and  may  be  many  degrees  below  the  air  tempera- 
ture, the  difference  between  the  two  temperatures  depending  upon 
the  relative  humidity  of  the  air — the  drier  the  atmosphere  the  lower 
the  sensible  temperature  when  compared  with  the  air  temperature ; 

236825  3 


the  damper  the  air  the  higher  the  sensible  temperature.  This  will 
be  better  understood  when  it  is  stated  that  in  case  the  air  be  satu- 
rated, the  readings  of  the  dry  and  the  wet  bulb  thermometers  will  be 
the  same  and  the  sensible  temperature  and  the  air  temperature  will 
be  equal.  In  the  semiarid  regions  of  the  West  the  sensible  tempera- 
ture during  the  summer  months  often  is  20°  to  30°  less  than  the  air 
temperature,  which  condition  is  due  to  the  extreme  dryness  of  the 
atmosphere.  In  the  more  humid  regions  of  the  eastern  part  of  the 
country  such  extreme  differences  can  not  occur. 

Gradually  the  publication  of  sensible  temperatures  has  been  ex- 
tended until  now  the  readings  of  the  wet-bulb  thermometer  appear 
on  all  published  maps  and  meteorological  tables  of  the  United  States 
Weather  Bureau  issued  from  its  many  stations.  Over  four  million 
maps  are  posted  annually  in  conspicuous  places  in  the  important 
cities  and  towns  of  the  country,  and  the  tables  are  printed  in  many 
of  the  large  dailies  of  the  principal  cities. 

The  publication  thus  made  of  the  thermal  conditions  of  the  United 
States  will  result  in  correcting  many  erroneous  impressions  in  regard 
to  the  climate  of  the  West  which  have  found  lodgment  in  the  minds 
of  those  accustomed  to  consider  only  the  air  temperature. 

To  present  anything  like  a  comprehensive  discussion  of  the  widely 
varying  thermal  conditions  of  the  United  States  and  a  comparative 
view  of  the  effects  of  solar  insolation  on  the  humid  sections  of  the 
East,  the  subarid  regions  of  the  middle  west,  and  the  arid  portions  of 
the  Rocky  Mountain  Plateau  necessitates  a  cursory  consideration  of 
the  climate  of  the  United  States  in  general  and  of  some  selected 
portions  of  foreign  countries. 

A  proper  understanding  of  the  climatic  conditions  of  the  region 
west  of  the  one  hundredth  ^parallel  jis  of  vast  importance,  not  only 
to  the  agricultural,  industrial,  hygienic,  and  therapeutic  interests  of 
the  many  states  represented  in  this  Congress,  but  of  the  United  States 
in  general.  That  which  is  of  vital  interest  to  a  part  should  be,  and 
in  this  case  is,  of  material  interest  to  the  whole. 

The  physical  characteristics  of  this  vast  region  and  its  geograph- 
ical boundaries  have  been  so  fully  described  elsewhere  that  it  is  not 
necessary  to  repeat  them  here.  A  word,  however,  regarding  the  ter- 
ritory under  discussion  may  not  be  amiss.  The  lands  west  of  the 
one  hundredth  meridian  are  generally  classed  as  arid,  or  semiarid, 
excepting  of  course,  considerable  portions  of  California,  Oregon,  and 
Washington,  and  mountainous  regions  of  these  and  other  States. 
The  dividing  line  between  arid  and  agricultural  lands  (using  the  lat- 
ter term  as  signifying  a  region  of  sufficient  rainfall  for  the  growth 
and  maturity  of  the  staple  crops)  is  not  strongly  marked.  Indeed 
no  inconsiderable  portion  of  several  States  west  of  the  Mississippi 
have,  at  irregular  intervals,  sufficient  rainfall  to  yield  bountiful  crops, 


NOTE. 


After  the  word  «  hundredth,"  17th  line  from  the  bottom,  page  4, 
read  "meridian"  instead  of  "parallel." 


but  in  a  majority  of  years  the  rainfall  is  below  the  needs  of  success- 
ful agriculture.  It  would  be  manifestly  improper  to  class  these 
lands  as  belonging  to  the  arid  regions  of  the  country ;  they  should 
rather  be  referred  to  as  regions  of  uncertain  rainfall  in  which  agri- 
cultural operations  without  irrigation  are  more  or  less  hazardous. 

Much  valuable  information  respecting  the  climate  and  resources  of 
the  arid  regions  has  been  collected  by  public-spirited  citizens  of  the 
Western  States  and  Territories.  In  the  following  remarks  an  attempt 
will  be  made  to  point  out  some  of  the  more  important  conclusions 
that  may  be  drawn  from  the  climatic  data  collected  both  by  private 
citizens  and  Government  officials. 

The  available  material  for  this  discussion  may^be  considered  in  a 
two-fold  sense,  viz :  first,  as  defining  the  climate  of  the  region,  par- 
ticularly with  reference  to  its  suitability  as  a  place  of  residence  for 
those  unable  to  withstand  the  rigors  of  the  climate  elsewhere,  and 
second,  in  its  relation  to  engineering  and  other  economic  projects. 

It  is  not  difficult  to  reach  a  proper  understanding  of  the  climates^ 
of  the  arid  region,  but  unfortunately  the  correlation  of  climatic  data 
and  vital  statistics  has  not  been  effected  as  fully  as  might  be  desired.) 
The  problem,  therefore,  is  not  completely  solved  by  an  examination 
of  the  climatic  statistics  alone.     It  is  admitted  by  those  eminent  in 
the  medical  profession  that  the  study  of  the  influence  of  the  various 
physical  elements  of  climate  upon  the  human  organism  and  the  col- 
lection of  morbidity  and  mortality  statistics  demand  the  careful 
attention  of  public  officials  and  the  active  cooperation  of  private 
citizens  in  whatever  sphere  they  may  be  found. 

General  meteorology,  especially  that  branch  pertaining  to  weather 
forecasting,  is  being  developed  as  rapidly  as  the  conservative  use  of 
means  and  appliances  at  hand  will  permit.  The  development  of  the 
physiologic  aspect,  however,  is  a  problem  of  much  wider  range,  and 
one  requiring  the  accumulation  of  a  vast  fund  of  statistics  outside 
the  realm  of  either  climatology  or  meteorology.  It  is  a  fact  to  be 
regretted  by  every  sincere  lover  of  knowledge  that  the  collection  of 
data  relating  to  the  classification  of  climates  with  reference  to  cer- 
tain diseases,  the  influence  and  special  dangers  of  various  climates 
upon  the  health  seeker,  and  other  matters  of  equal  importance  are 
not  coextensive  with  the  collection  of  weather  reports. 

The  present  elaborate  system  of  weather  reports  is  the  direct  result 
of  private  effort  and  investigation  fostered  by  the  Smithsonian  Insti- 
tution. Is  it  too  much  to  hope  that  the  facts  upon  which  the  science 
of  medical  climatology  must  depend  for  advancement  will  be  con- 
tributed by  the  private  worker?  « 

Within  the  broad  confines  of  the  United  States  there  are  many, 
but  not  all,  shades  and  varieties  of  climate.  One  of  the  questions 
most  frequently  asked  the  \Veather  Bureau  is,  "  Where  shall  I  find  a 


climate  possessing  both  dryness  and  equability  of  temperature ?" 
To  this  interrogatory  reply  must  be  made,  that  the  ideal  climate  as 
regards  equability  of  temperature  and  absence  of  moisture  does  not 
exist  in  the  United  States,  but  that  the  nearest  approach  to  it  will 
be  found  in  the  great  Southwest,  where  all  shades  of  dryness,  from 
a  rainfall  sufficient  for  successful  agriculture  to  the  aridity  of  the 
desert,  may  be  found. 

The  temperature  of  the  Southwest  is  not  equable  in  the  sense  of 
having  an  extremely  small  daily  range,  but,  on  the  other  hand,  it 
possesses  the  quality  of  uniformity  in  a  greater  degree  than  will  gen- 
erally be  found  elsewhere  except  on  the  seacoast.  The  most  equable 
temperature  on  the  globe  will  be  found  on  the  high  table-lands  and 
plateaus  of  the  Tropics.  Santa  Fe  de  Bogota,  in  the  United  States  of 
Colombia,  has  an  average  temperature  of  about  59°  for  all  months  of 
the  year,  and  the  range  for  the  entire  year  is  less  than  is  often  expe- 
rienced in  a  single  day  in  these  latitudes. 

But  while  the  ideal  temperature  may  be  found  on  the  higher  eleva- 
tions of  the  Tropics,  the  rainfall  is  much  greater  and  more  continuous 
than  in  this  country. 

The  rainfall  of  the  great  Southwest  varies  with  location.  Less 
I  than  200  miles  from  the  Colorado  Desert,  where  the  rainfall  is  prac- 
tically nil,  places  may  be  found  whose  annual  average  rainfall  is 
as  great  or  greater  than  any  point  in  the  Middle  States  of  the  East. 
Generally  speaking,  however,  the  greater  portion  is  dry,  using  that 
term  as  indicating  a  rainfall  considerably  less  than  20  inches  per 
annum  on  the  average. 

The  mountainous  portions  of  Arizona  and  California  have  an  aver- 
age annual  rainfall  ranging  between  20  and  50  inches,  depending 
somewhat  upon  the  elevation  and  geographic  position,  while  the  low- 
land portions  and  the  plateaus,  especially  east  of  the  Sierras,  have  a 
rainfall  both  small  in  amount  and  variable  in  character.  The  rain- 
fall records  of  the  arid  region,  and  other  portions  of  the  United 
States,  are  published  in  the  monthly  bulletins  of  the  various  climate 
and  crop  centers,  and  in  more  convenient  form  in  the  annual  data 
volumes  of  the  Weather  Bureau.  It  is  not  possible  to  report  upon 
them  in  detail  here. 

The  temperature  of  a  place  depends  chiefly  on  three  conditions, 
viz.,  latitude^elevation,  and  contiguity  toTar^^odje^of^water.  At 
sea  level  in~the  Tropics  extreme  condition^ of  heat  and~moisture  so 
combined  as  to  produce  very  great  physical  discomfort  abound.  But 
even  under  the  equator  it  is  possible  to  escape  the  tropical  heat  of 
low  levels  by  asceijding  from  4,000  to  6,000  feet.  In  the  economy  of 
nature  there  is  a  certain  limit  beyond  which  the  two  extremes,  dry- 
ness  and  equability  of  temperature,  can  not  coexist;  thus  we  may  find 
a  region  so  deficient  in  moisture  as  to  satisfy  the  requirements  of  the 


case,  but  the  very  lack  of  moisture  is  a  condition  that  facilitates 
radiation  and  thus  contributes  to  great  extremes  of  temperature. 
Regions  may  be  found,  as  on  the  lower  Nile,  where  there  is  a  lack  of  rain- 
fall coupled  with  a  high  and  moderately  uniform  temperature.  The 
mean  winter  temperature  of  Cairo,  Egypt,  is  56° ;  mean  summer  tem- 
perature, 83°  ;  a  range  from  winter  to  summer  of  27°.  The  mean  win- 
ter temperature  of  Phoenix,  Ariz.,  is  52° ;  mean  summer  temperature, 
87C ;  a  range  of  35°.  It  is  by  no  means  difficult  to  find  a  counter- 
part of  the  far-famed  Egyptian  climate  in  the  great  Southwest. 

The  dryness  of  the  air  and  the  clearness  of  the  sky  are  the^ 
conditions  upon  which  daily  ranges  of  temperature  depend;  the 
greater  these,  the  greater  the  range  of  temperature  from  day  to , 
night.  While  a  high  summer  temperature  is  characteristic  of  the 
Southwest  it  is  a  fact  long  known  to  residents  of  that  section, 
and  somewhat  imperfectly  realized  in  other  portions  of  the  coun- 
try, that  the  sensation  of  heat  as  experienced  by  animal  life  is 
not  accurately  measured  by  the  ordinary  thermometer.  The  sensa- 
tion of  temperature  which  we  usually  refer  to  the  condition  of  the 
atmosphere  depends  not  only  on  the' temperature  of  the  air,  but  also 
on  its  dryness,  the  velocity  of  the  wind,  and  other  circumstances. 
The  human  organism  when  perspiring  freely  evaporates  the  moisture 
of  its  surface  and  thus  lowers  its  temperature.  The  meteorological 
instrument  that  registers  the  temperature  of  evaporation  and  thus  in 
a  great  measure  the  actual  heat  felt  by  the  human  body,  is  the  wet 
bulb  thermometer.  The  latter  as  indicated  by  its  name  is  simply  an 
ordinary  mercurial  thermometer  whose  bulb  is  wetted  with  water  at 
the  time  of  observation. 

Chart  I  has  been  constructed  to  show  the  average  actual  and  sensi- 
ble temperatures  of  Weather  Bureau  stations  in  the  United  States  for 
the  summer  season. 

The  broad  principle  illustrated  by  this  chart  is  that  the  greatesf 
differences  between  shade  and  sensible  temperatures  are  found  where 
the  air  is  the  driest  and  the  least  where  the  air  is  most  humid. 
A  glance  at  the  chart  is  sufficient  to  show  the  general  trend  of  the 
lines  of  equal  air  and  sensible  temperatures.  The  great  interior  val- 
leys, and  the  plains  east  of  the  foothills  of  the  Rocky  Mountains  are 
uniformly  heated  under  the  insolation  of  summer  to  an  average  of 
from  65°  on  the  northern  boundary  to  about  80°  on  the  Gulf  Coast. 
The  northern  portion  of  this  vast  extent  of  country  is,  moreover,  in 
the  path  of  atmospheric  disturbances  that  pass  from  west  to  east 
over  our  northern  boundaries,  thus  causing  an  indraught  of  warm^/ 
moist  air  from  lower  latitudes.  Again,  the  distribution  of  atmos- 
pheric pressure  over  the  pnstprnj-,\rn-tVnrdH  of  the  United  States  is  at 
times  such  as  to  cause  a  more  or  less  complete  stagnation  of  the  i  * 
generally  eastward  drift  of  the  air ;  the  surface  of  the  ground  warms  [ 


8 

I  up  under  intense  insolation  and  loses  but  little  heat  by  radiation  at 
night ;  the  winds  are  light  southerly  or  southeasterly  and  there  is  an 
absence  of  vertical  interchange  between  the  warm  surface  air  and 
the  cooler  air  aloft.  Such  conditions  sometimes  extend  over  the  en- 
tire Mississippi  Valley  and  eastward  to  the  Atlantic  Seaboard.  On 
the  other  hand,  while  it  is  possible  for  a  heated  term  to  prevail  over 
an  arid  region  by  day,  the  relatively  great  radiation  by  night  lowers 
the  temperature  to  an  endurable  degree  and  there  is  but  little  bodily 
discomfort.  The  heat  of  the  daytime,  moreover,  is  borne  without 
distress  by  reason  of  the  great  dryness  of  the  air.  The  red  lines  of 
Chart  I  show  the  temperature  of  evaporating  surfaces  in  summer  in 
the  United  States.  It  will  be  seen  that  the  line  of  60°,  which  marks 
the  temperature  of  evaporation  of  the  region  of  New  England  and 
the  Great  Lakes,  passes  almost  due  north  and  south  along  the  eastern 
foothills  of  the  Rocky  Mountains,  and  skirts  southern  New  Mexico 
and  Arizona.  The  line  of  55°  passes  almost  due  south  from  eastern 
Montana  to  southeastern  New  Mexico  and  thence  northwesterly. 
The  temperature  of  evaporation  in  all  of  the  territory  above  this  line 
(55°),  embracing  almost  two-thirds  of  the  arid  region,  is  below  55°; 
in  fact,  in  almost  one-third  of  the  region  it  is  not  over  50°.  The 
sensible  temperature  of  two-thirds  of  the  United  States,  or  east  of  the 
one  hundred  and  fifth  meridian,  ranges  from  55°  to  75°.  West  of  the 
one  hundred  and  fifth  meridian  the  range  is  from  50°  to  65°. 

Chart  II  has  been  prepared  to  illustrate  the  extreme  differences 
that  prevail  in  midsummer,  the  8  p.  m.,  seventy-fifth  meridian  time 
observation  of  July  having  been  used.  (8  p.  m.,  seventy-fifth  meri- 
dian, corresponds  to  7  p.  m.  central,  6  p.  m.  mountain,  and  5  p.  m. 
Pacific  time).  There  is  an  objection  to  the  use  of  synchronous  time 
in  depicting  climatic  elements  that  have  a  marked  diurnal  period. 
Observations  taken  at  the  same  moment  of  local  mean  time  should 
be  used  whenever  possible,  but  the  exigencies  of  a  service  instituted 
for  the  purpose  of  forecasting  weather  changes  demand  the  use  of 
synchronous  time.  As  regards  the  data  of  this  chart  (II),  it  may  be 
urged  with  propriety  that  a  comparison  of  thermometric  readings 
made  at  the  same  moment  of  time  from  the  Atlantic  to  the  Pacific  is 
misleading,  since  an  accurate  estimate  can  not  be  made  of  the  amount 
of  increase  of  temperature  for  western  stations  due  to  diurnal  influ- 
ences alone,  and  it  was  mainly  with  a  view  of  illustrating  this  fact 
that  the  chart  was  prepared. 

The  thermometer  readings  on  the  Atlantic  Seaboard  are  made  near 
the  hour  of  8  p.  m.,  local  mean  time;  those  on  the  California  coast 
are  made  near  5  p.  m.,  local  mean  time.  Naturally  the  Pacific  Coast 
temperatures  are  considerably  higher  than  those  on  the  other  side  of 
the  continent,  three  hours  later  in  the  afternoon.  The  contrast  be- 
tween the  two  sides  of  the  country  is  plainly  shown  by  the  black 


lines  of  equal  actual  temperature  on  Chart  II,  and  it  will  also  be 
observed  that  the  Southwest  is  the  warmest  part  of  the  United  States. 

The  lines  of  equal  sensible  heat,  on  the  other  hand,  show  an  en- 
tirely different  condition  as  regards  the  location  of  greatest  heat. 
The  arid  region  is  now  the  coolest  part  of  the  United  States,  judged 
from  the  temperature  of  evaporation  only.  The  line  of  60°  sensible 
temperature,  starting  in  New  England,  skirts  the  northern  boundary 
as  far  as  the  one  hundred  and  tenth  meridian ;  thence  it  follows  a 
south-southeasterly  course  to  southeastern  New  Mexico ;  thence  west- 
erly to  the  neighborhood  of  Los  Angeles,  Cal.,  and  thence  northerly, 
with  a  few  unimportant  deflections,  to  the  north  Pacific  Coast. 

The  decrease  of  temperature  from  the  hour  of  maximum  heat  to- 
nightfall  is  not  regular,  nor  does  it  bear  any  definite  relation  to  an 
increase  in  longitude  reckoned  westward  from  Greenwich.  A  com- 
parison of  the  normal  8  p.  m.  seventy-fifth  meridian  time  tempera- 
tures with  the  normal  maximum  temperature  of  the  day  shows  that 
on  the  eastern  coast  line  the  temperature  at  8  p.m. is, on  the  average, 
8°  to  12°  lower  than  at  the  time  of  greatest  daily  heat.  In  the  Lake 
Region  and  lower  Ohio  Valley  the  difference  is  from  5°  to  8°.  In 
the  upper  Mississippi  and  Missouri  valleys  and  Texas  and  the  plains 
region  the  difference  averages  from  4°  to  7° ;  that  is  to  say,  the  tem- 
peratures at  the  8  p.  m.  observation  (corresponding  to  about  6.30 
p.  m.,  local  time)  are  from  4°  to  7°  lower  than  the  highest  point 
reached  by  the  thermometer  during  the  day.  On  the  eastern  slope 
of  the  Rocky  Mountains,  although  the  evening  observation  is  made 
at  6  p.  m.,  local  time,  two  hours  nearer  the  time  of  greatest  heat  than 
at  New  York  and  Philadelphia,  the  difference  is  as  great  as  at  the 
last-named  places.  In  other  words,  the  temperature  falls  as  much 
by  6  p.  m.  at  Denver  as  it  does  by  8  p.  m.  in  New  York  and  Phila- 
phia.  This  would  seem  to  be  the  result  of  the  greater  daily  range 
and  more  rapid  rate  of  cooling  at  elevated  stations.  West  of  the 
Rockies  the  differences  range  from  zero  at  Red  Bluff  to  less  than  4° 
in  the  great  interior  basin  and  from  5°  to  6°  in  southern  Arizona. 

The  local  vicissitudes  of  temperature  are  well  illustrated  in  the 
case  of  Red  Bluff,  Cal.,  where  the  average  temperature  at  about  5  p. 
m.,  local  time,  is  but  four-tenths  of  a  degree  below  the  maximum  of 
the  day.  Curiously  enough,  at  Los  Angeles,  in  the  lower  part  of  the 
State,  the  5  p.  m.  temperatures  are  about  10°  lower  on  the  average 
than  the  maximum  of  the  day. 

Chart  III  has  been  constructed  to  show  the  relative  humidity  of 
the  United  States  in  summer.  The  data  used  in  preparing  the  chart 
were  the  synchronous  observations  at  8  a.  m.  and  8  p.  m.,  seventy- 
fifth  meridian  time,  during  the  eight  years  1889-96.  The  chart  itself 
shows  better  than  mere  words  the  distinctively  dry  and  humid  regions. 
The  influence  of  the  ocean  is  seen  on  both  coasts,  as  also  that  of  the 
Gulf  of  Mexico  and  the  Great  Lakes. 


10 

Broadly  speaking,  the  variation  of  insolation  from  day  to  night, 
and  from  season  to  season,  with  the  changing  declination  of  the  sun, 
is  the  great  controlling  agent  of  climate.  The  most  regular,  and  at 
the  same  time  the  simplest  climate  of  the  world,  is  that  of  the  Tropics, 
where  the  succession  of  changes  from  day  to  day  are  as  monotonous 
in  their  regularity  as  they  are  enervating  on  the  human  system.  The 
great  life  zone,  the  seat  of  business  enterprise  and  activity,  is  found 
in  temperate  climates.  Here  the  simple  diurnal  changes  of  the 
Tropics  are  largely  masked  by  irregular  changes,  the  result  of  the 
passage  of  cyclonic  and  anticyclonic  systems.  The  sum  total  of  these 
•changes  constitutes  the  weather  of  the  temperate  zone. 

Between  the  Tropics  and  the  temperate  zone  there  are  in  certain 
longitudes  considerable  areas  where  the  climate  is  more  or  less  tran- 
sitional between  the  two  strongly  marked  zones.      The  southwestern 
part  of  the  United  States  may  be  classed  as  having  a  climate  between 
the  extremes  of  the  Tropics  and  the  temperate  zones.   Not  being  within 
the  path  of  storm  frequency,  the  sequence  of  weather  is  more  uni- 
form than  in  more  northern  latitudes,  or  on  the  same  parallel  farther 
•east.     The  rainfall  is  deficient ;  there  is  an  absence  of  clouds ;  insola- 
tion by  day  and  radiation  by  night  are  both  strong ;   the  range  of 
temperature  from  day  to  night  is  large,  from  25°  to  35°,  depending 
upon  the  elevation  and  character  of  the  surface  of  the  ground ;  the 
winds  are  generally  light  and  the  evaporation  is  high. 
/    The  climatic  data  collected  by  the  Weather  Bureau,  viewed  from 
/  an  economic  standpoint,  are  mainly  valuable  as  giving  definite  infor- 
I    mation  of  the  monthly  and  annual  amounts  of  rainfall,  the  maxi- 
\    mum  and  minimum  amounts  in  varying  periods  of  time,  the  distri- 
V  bution  throughout  the  year,  and  the  secular  variation. 

It  is  not  proposed  to  enter  into  a  discussion  of  the  rainfall  records, 
nor  of  the  closely  related  subject  of  evaporation  from  a  water  surface. 
The  last-named  subject  is  one  that  requires  careful  experimental  work 
with  a  view  of  determining  what  form  of  evaporometer  is  best  adapted 
to  the  requirements  of  the  case.  The  conditions  under  which  obser- 
vations of  evaporation  could  be  made  at  Weather  Bureau  stations  are 
largely  artificial,  and  it  is  doubted  if  results  of  scientific  or  practical 
value  could  be  obtained  therefrom. 

The  use  of  windmills  for  pumping  and  storing  water  is  quite  com- 
mon both  in  humid  and  in  arid  regions ;  in  the  latter,  however,  the 
successful  application  of  the  forces  of  the  wind  to  the  raising  of  water 
for  irrigating  purposes  is  a  much  more  important  matter  than  else- 
where. Irrigable  land,  so  situated  that  the  water  of  natural  streams 
can  not  be  diverted  thereto,  must  depend  upon  the  flow  of  artificial 
reservoirs,  and  these  latter  in  turn  must  be  supplied  from  the  under- 
ground flow.  When  the  static  pressure  on  the  surface  of  the  latter 
is  not  sufficient  to  force  the  water  to  the  surface,  resort  must  be  had 


11 

to  pumping.  The  economy  of  the  wind  as  a  motive  power  can  not 
be  questioned ;  but,  on  the  other  hand,  its  use  is  restricted  to  such 
classes  of  work  as  will  admit  of  temporary  cessation  during  a  calm. 
A  knowledge  of  the  strength  of  the  surface  winds  is  essential  to  a 
thorough  understanding  of  the  limits  and  possibilities  of  windmills 
in  connection  with  irrigation  problems. 

The  strength  of  the  surface  winds  over  the  arid  region  varies 
greatly  on  account  of  the  broken  configuration  of  the  land  and  its 
-geographic  position  with  respect  to  the  path  of  cyclones  and  anti- 
cyclones. Surface  winds  are  purely  the  result  of  unequal  pressure 
•distribution  over  adjacent  areas.  The  winds  blow  from  a  region  of 
high  pressure  to  a  region  of  low  pressure,  and  the  steeper  the  gradient 
the  faster  they  blow.  The  velocity  of  the  lowest  stratum  of  air  is 
greatly  retarded  by  friction  on  the  surface  of  the  earth,  the  retarding 
effect  being  most  noticeable  in  the  layer  of  air  extending  from  the 
surface  of  the  ground  to  fifteen  feet  above  it. 

It  is  exceedingly  difficult  to  combine  wind  data  of  meteorological 
•observatories  into  a  homogeneous  system.  The  influence  of  a  border- 
ing range  of  hills  or  of  adjoining  buildings  may  seriously  vitiate  the 
record.  Accurate  comparisons  of  wind  velocities  can  not  be  made, 
on  account  of  the  lack  of  uniformity  in  the  elevation  of  ane- 
mometers, except  by  the  application  of  a  system  of  instrumental 
corrections.  Such  a  system  of  corrections  has  not  been  applied, 
nor  have  actual  velocities  been  reduced  to  true  velocities  in  any  case. 
A  comprehensive  presentation  of  the  wind  velocities  of  any  region 
should  include  a  statement  of  the  average  hourly  velocities  for  the 
several  months  of  the  year ;  of  the  strength  of  gust  velocities  for 
short  intervals ;  of  the  diurnal  and  seasonal  changes ;  and,  as  par- 
ticularly appropriate  to  the  subject  of  these  remarks,  a  statement  of 
the  number  of  hours  in  each  month  of  available  wind  power,  say  of 
wind  velocities  from  6  to  10  miles;  11  to  15  miles,  etc.  The  average 
hourly  velocities  for  a  number  of  stations  west  of  the  one  hundredth 
meridian  have  been  computed  and  will  be  found  in  Table  I.  These 
data  express  the  average  force  of  the  wind  as  shown  by  anemometers 
exposed  on  Weather  Bureau  buildings  in  the  places  named  for  the  eight 
years  ended  with  1895.  The  averages  have  been  made  from  the  record 
for  the  twenty-four  hours  and  include,  as  will  be  more  fully  shown 
later,  periods  when  the  velocity  is  above  the  average  as  well  as  below  it. 
It  is  apparent  that  the  region  of  greatest  velocity  of  the  wind  or 
greatest  windiness  is  in  Kansas,  Oklahoma,  Texas,  and  Nebraska, 
some  distance  east  of  the  foothills  of  the  Rocky  Mountains.  The 
slope  of  this  area  is  to  the  eastward ;  its  surface  offers  compara- 
tively little  resistance  to  the  winds ;  the  barometric  gradients  are 
moderately  steep,  except  during  the  summer  season.  In  the  latter 
season  the  air  of  the  plains  becomes  heated  and  rarified  and  a  strong 


12 

vertical  circulation  is  established  and  the  air  of  surrounding  regions 
is  drawn  in,  thus  maintaining  active  air  circulation  at  a  time  when 
the  pressure  gradients  are  weakest. 

The  variation  in  velocity  during  the  year  is  graphically  shown  be- 
low in  Fig.  1,  the  curve  "  a  "  representing  the  plains  group. 

In  the  diagram  just  mentioned  the  months  of  the  year  are  repre- 
sented by  vertical  divisions ;  the  velocity  of  the  wind  in  miles  per  hour 
by  the  horizontal  divisions,  each  of  which  represents  a  mile  of  wind. 

The  three  curves  show  the  average  hourly  wind  velocity  for  each 
month  of  the  year  in  three  separate  regions,  viz.,  (1)  the  great  plains- 
extending  from  the  Dakotas  to  Texas;  (2)  the  Rocky  Mountain  re- 
gion, including  the  States  of  Wyoming,  Colorado,  and  New  Mexico, 
and  (3)  Arizona. 

The  curves  are  alike  in  their  general  characteristics,  and  it  is  quite- 
evident  that  they  are  all  modifications  of  one  simple  type. 

The  plains  type  is  believed  to  be  the  fundamental  one.  Here  by 
reason  of  the  surface  configuration  there  is  little  friction  on  the  earth's 
surface ;  the  sweep  of  the  wind  is  not  broken  by  forests  or  other  ob- 
structions, and  the  high  average  velocities  attained  lead  us  to  believe- 
that  the  annual  march  of  the  wind  is  much  the  same  as  would  obtain 
on  a  water  surface.  It  should  be  remembered  that  the  wind  veloci- 
ties observed  on  the  great  plains  are  almost  as  high  as  prevail  at  ex- 
posed stations  on  the  seacoast.  There  is  an  abundance  of  wind  for 
driving  windmills  as  will  be  shown  by  the  statistics  of  Table  II. 

The  curves  in  Fig.  1  show  a  maximum  of  wind  in  April  and  a  mini- 
mum in  August,  and  this  characteristic  is  common  to  all  sections  of 
the  arid  region  except  the  interior  valleys  of  California  where  the- 
spring  maximum  is  deferred  until  May  and  June. 

The  coast  winds  of  California  differ  in  some  respects  from  those  of 
the  interior.  They  are  principally  from  some  westerly  quarter,  quite- 
steady  and  strong  in  summer,  especially  in  the  region  of  San  Fran- 
cisco, giving  to  the  coast  a  climate  much  colder  than  some  miles  in- 
land. The  effect  of  these  westerly  winds  is  plainly  seen  on  Charts  I,. 
II,  and  III. 

The  foregoing  relates  especially  to  the  relative  strength  of  the  winds- 
in  the  different  months  of  the  year.  Considering  now  the  relative 
velocities  of  different  localities  as  shown  by  the  three  separate  types, 
it  is  observed,  first,  that  the  winds  of  high  stations,  such  as  Cheyenne, 
Denver,  and  Santa  Fe,  are  not  as  strong  as  might  naturally  be  ex- 
pected. It  is  true  that  wind  velocities  increase  both  with  elevation 
above  ground  and  with  elevation  above  sea,  but  the  increase  does  not 
depend  upon  elevation  alone,  nor  does  it  increase  in  direct  proportion 
to  the  increase  in  elevation.  The  winds  of  Mount  Washington  are- 
much  stronger  than  those  of  Pikes  Peak,  although  the  latter  is  more- 
than  double  the  altitude  of  the  former. 


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13 

The  diminution  of  the  average  velocity  of  the  wind,  as  shown  in 
curves  b  and  c.  Fig.  1,  may  be  ascribed  in  a  great  measure  to  the  in- 
equalities of  the  land  surface,  although  there  are  doubtless  other 
causes  that  contribute  to  the  general  retardation.  In  a  region  of 
great  contrasts  of  surface  configuration,  moreover,  the  number  of 
faulty  anemometer  exposures  is  relatively  greater  than  in  a  region  of 
comparatively  even  surface.  In  the  latter  case,  the  only  condition 
required  is  that  the  anemometers  be  placed  at  a  uniform  level  above 
the  street.  And  in  case  they  are  not  of  uniform  elevation  we  may 
apply  a  correction  to  the  recorded  velocities  in  order  to  reduce  them 
to  some  standard  height  above  ground.  As  illustrating  the  increase 
of  velocity  with  elevation  above  ground,  the  case  of  El  Paso,  Tex., 
may  be  cited.  The  anemometer  at  this  station  was  exposed  for  ten 
years  at  an  average  elevation  of  30  feet  above  ground,  and  the  aver- 
age annual  wind  movement  for  the  same  period  was  41,000  miles,  or 
at  the  rate  of  4.7  miles  per  hour. 

An  increase  of  elevation  to  80  feet  gave  an  average  annual  wind 
movement  of  71,000,  or  at  the  rate  of  8  miles  per  hour,  almost  double 
the  velocity  at  the  low  elevation. 

A  description  of  some  experiments  made  by  Mr.  Thomas  Steven- 
son to  determine  the  relative  velocity  of  the  wind  at  different  heights 
above  ground,  will  be  found  in  the  Journal  of  the  Scottish  Meteoro- 
logical Society  from  which  the  drawing  below,  Fig.  2,  is  reproduced. 

With  low  velocities  the  change  with  altitude  up  to  50  feet,  the  high- 
est elevation  at  which  the  experiments  were  made,  was  not  great. 
Thus,  a  velocity  of  10  miles  per  hour  at  5  feet  above  ground  became 
13  miles  at  50  feet.  With  the  higher  velocities,  however,  the  increase 
was  much  more  rapid,  a  velocity  of  20  miles  per  hour  at  5  feet  above 
ground  becoming  37  miles  at  50  feet. 

The  formula  proposed  by  Stevenson  for  finding  the  velocity  Fat 
any  point,  H  feet  above  ground,  from  the  known  velocity  v  at  a 
height  h  feet  above  ground  (h  being  above  15  feet),  is 


v 

\  h  +  72 

Using  the  known  velocities  at  Weather  Bureau  stations,  we  may 
•compute  from  this  formula  the  velocities  that  should  prevail  at  the 
elevation  of  the  windmill  driving  arms  above  ground.  A  second 
-conclusion  of  no  less  importance  is  that  in  order  to  obtain  the  maxi- 
mum efficiency  of  the  wind  in  regions  of  low  average  velocity,  it  is 
necessary  to  place  the  driving  arms  at  a  much  higher  elevation  than 
in  regions  of  high  velocity. 

The  velocity  of  the  winds  in  Arizona,  the  Great  Basin,  and  the 
interior  valleys  of  California,  on  the  average  of  the  year,  does  not 
vary  greatly  from  about  6  miles  per  hour.  This  value,  however,  in- 
cludes varying  periods  of  greater  and  less  velocities. 


14 

The  average  wind  velocity  is  chiefly  useful  in  determining,  in  a  gen- 
eral way  the  practicability  of  using  the  wind  as  a  motive  power.  In 
India,  for  example,  an  examination  of  the  recorded  wind  velocities 
shows  at  a  glance  that  windmills  can  not  be  employed  except  at  a  few- 
places  during  the  height  of  the  summer  monsoon. 

The  average  velocities  for  certain  portions  of  the  arid  region,  given 
in  Table  I,  indicate  clearly  that  during  a  part  of  the  time  the  wind 
is  not  sufficiently  strong  to  drive  an  ordinary  windmill.  How  much 
wind  is  available  on  the  average  can  be  determined  by  a  tabulation 
of  the  continuous  records  according  to  a  scale  of  progressive  veloc- 
ities. Thus  it  may  be  assumed  that  all  winds  of  5  miles  an  hour  and 
under  are  inefficient,  and,  on  the  other  hand,  that  winds  of  26  miles 
an  hour  and  upward  are  too  violent  for  practical  use.  We  have, 
therefore,  as  the  effective  winds  those  ranging  in  velocity  from  6  to 
24  miles  per  hour. 

Table  II  shows  for  six  stations,  Dodge  City,  North  Platte,  Pueblo, 
Lander,  Salt  Lake  City,  and  Yuma,  the  percentage  of  time  during 
the  five  years  1889-1893  (except  at  Lander,  where  a  period  of  three 
years  was  used),  that  hourly  velocities  of  0-5  miles  per  hour,  6-10,. 
11-15,  16-20,  21-25,  26-30,  and  31  and  upward  prevailed.  Had  time 
permitted,  the  data  for  a  greater  number  of  stations  would  have  been 
tabulated. 

The  greatest  amount  of  available  wind,  as  elsewhere  indicated  in  this 
paper,  is  found  on  the  plains  from  Texas  to  the  Dakotas.  The  two 
points  selected  to  represent  this  region,  Dodge  City,  Kans.,  and  North 
Platte,  Nebr.,  have  an  excellent  anemometer  exposure,  both  instru- 
ments being  52  feet  above  ground.  The  surface  of  the  surrounding 
country  is  generally  flat  and  treeless,  and  there  are  no  obstructions 
to  the  free  sweep  of  the  winds. 

At  Dodge  City  the  winds  during  72  per  cent  of  the  time  ranged  in 
velocity  from  6  to  25  miles  per  hour.  Assuming  that  the  use  of  wind- 
mills is  restricted  to  winds  of  6  to  15  miles  per  hour,  then  they  may 
be  employed  51  per  cent  of  the  time.  It  is  manifest,  however,  that 
higher  velocities  may  be  used  with  safety. 

The  results  at  North  Platte  agree  quite  closely  with  those  just 
mentioned.  High  velocities  at  the  last-named  station  are  not  so 
prevalent  as  at  Dodge  City,  yet  the  percentage  of  effective  winds  is 
about  the  same. 

There  is  a  popular  conception  that  of  all  meteorological  elements 
the  wind  is  the  most  fickle.  A  study  of  the  figures  in  the  table  will 
doubtless  lead  to  a  different  conclusion. 

The  general  agreement  between  the  percentages  of  the  two  stations 
is  reasonably  conclusive  evidence  that  such  percentages  truly  repre- 
sent the  actual  wind  movement  of  the  greater  portions  of  western. 
Kansas  and  Nebraska. 


15 

Pueblo,  Colo.,  in  the  Arkansas  River  Valley,  elevation  4,653  feet 
above  sea  level,  was  selected  as  representative  of  eastern  Colorado, 
where  irrigation  is  extensively  practiced.  Although  the  altitude  of 
Pueblo  is  2,176  feet  greater  than  Dodge  City,  the  total  wind  travel  is- 
36  per  cent  less  and  the  total  effective  winds  (6-25  miles  per  hour) 
but  49  per  cent  against  72  per  cent  at  Dodge  City.  It  is  important 
to  note,  however,  that  the  percentage  of  wrinds  of  low  velocities  (6-10) 
is  practically  the  same  at  both  stations,  30  and  29,  respectively. 
The  great  difference  between  the  two  points  being  in  the  higher 
velocities. 

The  Weather  Bureau  station  at  Lander,  in  the  Popo  Agie  Valley  r 
seven  miles  east  of  the  Big  Wind  River  chain  of  the  Rocky  Moun- 
tains, has  been  in  operation  but  a  few  years. 

The  velocities  are  unusually  low,  effective  winds  prevailing  only 
24  per  cent  of  the  time.  The  average  for  April,  May,  and  June,  how- 
ever, is  33  per  cent,  the  highest  of  the  year.  The  low  velocities  at 
this  station  are  doubtless  due  to  the  sheltering  influence  of  the  moun- 
tains to  the  westward  and  the  low  exposure  of  the  anemometer,  3£ 
feet  above  ground. 

The  winds  of  the  Great  Basin  are  not  truly  presented  by  the  instru- 
mental records  of  Salt  Lake  City,  the  immediate  environment  of  the 
latter  being  such  as  to  vitiate  the  record  in  a  greater  or  less  degree. 
A  spur  of  the  Wasatch  range,  but  3  miles  distant  to  the  eastward,. 
shelters  the  city  both  on  the  east  and  southeast.  On  the  north  hills 
rise  to  an  elevation  of  1,000  to  2,000  feet  above  the  city,  while  Great 
Salt  Lake  is  but  10  miles  distant  to  the  northwest.  The  combined 
influence  of  the  mountains  and  the  lake  produces  a  regular  diurnal 
period  except  when  overcome  by  the  stronger  gradients  of  atmospheric 
disturbances  to  the  northward.  The  winds  of  the  forenoon  are  from 
the  southeast  (the  mountains)  and  of  the  afternoon  from  the  north- 
west (from  the  lake).  Notwithstanding  the  faulty  exposure  of  the 
wind  instrument  at  Salt  Lake  City,  there  appears  to  be  sufficient 
wind  to  drive  a  windmill  34  per  cent  of  the  time.  High  winds  are 
unusually  rare. 

The  percentage  of  effective  winds  at  Yuma,  Ariz.,  is  49  out  of  a 
probable  100.  The  winds  of  Arizona  differ  from  those  of  many  other 
portions  of  the  United  States  in  that  there  is  a  greater  daily  range 
and  less  interference  with  the  regular  progression  from  morning  to 
night  by  cyclonic  storms.  The  winds  of  the  nighttime  fall  to  a  very 
low  velocity,  but  those  of  the  daytime  are  quite  strong,  especially  on 
the  higher  plateaus,  where  an  average  of  12  to  14  miles  per  hour  is 
maintained  during  the  warm  season. 

The  anemometer  at  the  Yuma  station  is  about  50  feet  above  ground 
and  100  feet  distant  from  the  Colorado  River.  The  location  is  not 
as  advantageous  as  might  be  chosen  if  a  high-wind  velocity  were 


16 

the  only  desideratum,  but  it  is  similar  to  a  majority  of  the  locations 
in  which  windmills  would  naturally  be  placed,  and  for  that  reason 
the  data  are  applicable  to  the  problem  in  hand. 

The  average  wind  velocities  heretofore  published  for  Phoenix,  Ariz., 
were  determined  from  the  record  of  an  anemometer  exposed  19  feet 
above  ground.  When  the  station  was  reestablished,  in  August,  1895, 
the  anemometer  was  placed  57  feet  above  ground.  The  velocities 
obtained  in  the  new  location  are  considerably  higher  than  those 
in  the  old  location,  the  monthly  average  being  about  5  miles  per 
hour.  While  greater  velocities  generally  prevail  during  the  warmer 
hours  of  the  day,  there  will  be  occasions  in  the  daytime  when  the 
wind  will  fall  below  the  effective  limit.  The  remedy  in  such  cases  is 
a  higher  exposure  of  the  windmill. 

Summarizing  the  foregoing  in  a  few  words,  it  may  be  said  that 
there  is  an  abundance  of  effective  wind  on  the  plains  east  of  the 
Rocky  Mountains  in  all  months  of  the  year  and  that  no  special 
adaptation  of  the  ordinary  windmill  is  necessary. 

The  amount  of  effective  wind  decreases  with  approach  to  the 
Rocky  Mountains,  but  in  well-exposed  localities  there  is  still  suffi- 
cient for  all  ordinary  needs.  On  the  leeward  side  of  a  mountain 
range  and  in  sheltered  valleys  it  will  be  necessary  to  increase  the 
elevation  of  the  windmill  support  in  order  to  obtain  sufficient  wind 
for  pumping  purposes.  In  Arizona,  New  Mexico,  the  interior  valleys 
of  California,  and  the  Great  Basin  there  is  generally  sufficient  wind 
for  ordinary  purposes,  but  in  certain  locations  it  will  be  necessary  to 
select  a  favorable  position  for  the  windmill  and,  as  in  the  Rocky 
Mountain  Region,  to  place  the  driving  arms  at  as  great  an  elevation 
above  ground  as  may  be  practicable. 

Periods  of  calm  or  of  ineffective  velocities  occur  on  an  average 
once  or  twice  every  month  during  the  season,  April  to  September. 
The  duration  is  seldom  longer  than  twenty-four  hours ;  in  extreme 
cases  they  may  continue  forty-eight  hours. 


17 

TABLE  I. — A  i-erage  hourly  Telocity  of  the  wind  at  selected  stations  of  the  Weather  Bureau. 


Stations. 

| 

February. 

March. 

f 

<5 

| 

© 

= 
- 

-j 

>. 

p 

Ha 

August. 

September. 

October. 

Norember. 

fe 
£ 

Bismarck,  X.  Dak  
Huron  8  Dak 

9-0 
11.2 
8.2 
9.5 
8.5 
7.1 
9-9 
9.0 
16.3 
10.2 
8.0 

10.2 
12.6 
8.3 
10.3 
9.4 
8.1 
10.8 
10.5 
16.7 
12.4 
9.9 

10.5     12.8     12.1 
12.9     14.7     13.8 
9-6     10-6     10.2 
11.6     13.4     12.2 
10.8     12.6      11.8 
9.6     10.5       9.6 
12.  s     U.t     13.7 
11.9     11.4     10.2 
19.2     20.6     18.9 
13.3     13.2     12.  !» 
11.4     11.3     10.5 

10-6 
13.3 
10.0 
12.2 
10.9 
8-0 
13.8 
9.1 
18.8 
12.0 
8.8 

9.4 
10.3 
9.1 
10.3 
9.0 
6.9 
11.8 
7.8 
16.1 
9.6 
7.5 

9.1 
11.6 
8.4 
9.5 
8.6 
6.0 
10.9 
6.5 
13.4 
8.2 
7.5 

10.8 
13.7 
9.5 
10.9 
9.3 
7.0 
11.9 
9.0 
16.9 
9.5 
7.2 

10.5 
12.7 
9.2 
10.5 
8-8 
6.6 
10.4 
8.8 
16.2 
10.0 
7.2 

9.4 
11.9 
8.8 
10.4 
8.8 
7.3 
8.9 
9.4 
16.4 
10.5 
8.2 

8.8 
11.6 
8.4 
9.5 
8.2 
7.7 
10.4 
9.7 
16.2 
11.2 
8  4 

Rapid  City,  S.  Dak.  .  .. 
Valentine,  Xebr  
North  Platte,  Nebr  .  . 
Concorclia  Kans  

Dodge  City,  Kans.  .   . 
Oklahoma.  Okla  
Amarillo.  Tex  .     . 
\bilene  Tex 

El  Paso  Tex  

Mean 

9.7 

4.0 
12.4 

10.8 

3.6 
12.5 
7.4 
8.0 
7.3 
8.9 
5.4 

7.6 

11.4 
5.0 
4.6 
6.8 
5.5 

6.7 

7.6 
3.7 
11.6 
5.0 

7.0 

7.2 
6.2 

6.8 
6.9 

5.7 
4.7 
2.4 

4.3 

•  7.6- 
7.7 
4.8 
5.9 

G.5 

12.1 

5.2 
12.8 
8-1 

8.  7 
8.2 
8.4 
5.9 

8.2 

10.4 
7.0 
5-6 
7.5 
5.7 

7.2 

9.7 
5.0 
10.9 
6.3 

8.0 

7-1 
6.9 
7.0 
6.2 

6.8 

6.6 
5.0 
2.9 

4.8 

•8.0 
7.7 
5.8 
5.8 

6.8 

13.2 

5.6 
11.8 
8.6 
9.4 
8.3 
8.6 
6.9 

8.5 

10.8 
8.2 
6.3 
7.8 
6.2 

7.9 

9.0 
5.2 
11.4 
6.5 

8.0 

9.0 
8.5 

7.7 
7.1 

8.1 

6.9 
5.3 
3.6 

5.3 

'  7.4 
7.8 

6.8 
6-4 

7-1 

12.4 

5.5 
10.8 
7.9 
8.9 
8.4 
7.9 
7.3 

8.1 

10.5 
8.0 
6.5 
8.0 
5.6 

7.  7 

8.4 
4.3 
10.6 
6.5 

7.4 

8.6 
8.0 
7.4 
6.6 

7.6 

6.5 
5.5 
3.4 

5.1 

•  7.8 
8.5 
7.5 
6.2 

7.5 

11.6 

5.5 
10.0 
7.2 
8.2 
7.9 
6.3 
7.4 

7.5 

9.6 
7.1 
6.3 
7.6 
5.3 

7.1 

8.1 
4.1 
10-0 
6.4 

7.2 

8.8 
7-6 
7.0 
6.2 

7.4 

6.5 
5.2 
3.6 

5.1 

'  7.2 
8.6 
8.5 
6.3 

7.6 

9.8 

4.7 
9.0 
6.6 
7.2 
6.7 
4.5 
6.1 

6-4 

10.0 
6.2 
5.4 
7.2 
5.3 

6.8 

7.8 
3.6 
9.6 
5.8 

6.7 

6.9 
6.0 
6.0 

7.0 

6.5 

6.1 
5.1 
3.8 

5.0 

•5.8 
7.7 
7.2 
5.8 

6.6 

9.1 

4.0 
7.9 
6.4 
6.5 
5.9 
4.8 
5.7 

5.9 

8.7 
5.0 
4.7 
6.8 
5.4 

6.1 

7.2 

2.9 
9.0 
5.6 

6.2 

6.2 
5.6 
5.8 
6.1 

5.9 

5.3 
4.5 
3.3 

4.4 

•4.8 
6.9' 
6.4 
5.5 

5.9 

10.5 

5.0 
9.1 
6.4 
6.4 
6.1 
4.6 
5.8 

6.2 

10.0 
5.5 
5.2 
7.1 
5.4 

6.6 

8-3 
3.0 
9.4 
5.7 

6-6 

6.2 
6.1 
7.2 
4.8 

6.1 

5.3 
4.9 
2.9 

4.4 

•6.3 
7.0 
5.9 
5.5 

6.2 

10.1 

3.7 
10.1 
6.8 
6.5 
6.5 
5.5 
5.2 

6.3 

10.9 
5.7 
4.8 
7.4 
5.5 

6.9 

6.9 
3.3 
9.2 
5.0 

6.1 

6.3 
6.3 
6.9 
4.6 

6.0 

5.0 
4.2 
2.3 

3.8 
'6.3 

« 

5.1 
5.6 

10.0 

4.1 
11.4 
7.3 
6.6 
6.5 
5.4 
4.6 

6.6 

12.1 
6.1 
4.8 
7.1 
5.5 

7.1 

7.6 
3.2 
9.6 
4.6 

6.2 

5.3 
5.2 
6.6 
5.4 

5.6 

5.3 
4.5 
2.2 

4.0 

'6.6 
5.8 
3-7 

4.7 

5.2 

10.0 

4.0 
12.0 
7.3 
7.3 
6.6 
6.2 
4.3 

6.8 

11.9 
5.7 
5.3 
6.3 
5.6 

7.0 

7.0 
3.7 
10.0 

4.8 

6.4 

6-0 
5.1 
6-5 
5.8 

5.8 

6.0 
5.2 
2.4 

4.5 

1  6.8 
7.3 
4.2 
4.9 

5.8 

Cheyenne  Wyo  

Pueblo,  Colo  
Santa  Fe.  N.  Mex  
Fort  Stanton.  X.  Mex.  .  . 
Montrose  Colo  

7.4 
6.7 
6.3 
4.6 

7.0 

11.4 
5.2 
4.2 
5.3 
5.6 

6.3 

8.2 
3.4 
9.8 
4.5 

6.4 

5.5 
5.2 
6.6 
6.3 

5.9 

5.3 
5.2 

2.8 

4.4 

7.2 
7.0 
4.1 
5.0 

5.8 

Mean  

Havre  Mont  

Miles  Citv  Mont.  .. 

Helena,  Mont  
Baker  City  Oreg 

Mean 

Idaho  Fall*  Idaho  

Boise  City,  Idaho  
Winnemucca,  Nev  
Salt  Lake  City.  Utah  ... 

Mean  
Prescott  Ariz  

Fort  Apache,  Ariz  
Fort  Grant  Ariz  

Yuma,  Ariz  
Mean  

Walla  Walla.  Wash  .... 
Portland  Oreg. 

Mean 

Bed  Bluff,  Cal  
Sacramento.  Cal  
Fresno  Cal  

San  Diego,  Cal  
Mean  . 

18 

TABLE  II. — Summary  of  wind  movement,  in  percentages,  for  the  years  1889-93. 

DODGE  CITY,  KANS. 

(Elevation  above  sea,  2,477  feet;  anemometer  above  ground,  52  feet.i 


Miles  per  hour. 

0-5. 

6-10. 

11-15. 

16-20. 

21-25. 

26-30. 

2 
3 
4 
6 
5 
7 
3 
2 
5 
3 
2 
2 

4 

31+ 

1 
1 
3 
6 
4 
4 
1 
1 
3 
2 
2 
1 

2 

27 
26 
17 
16 
16 
17 
19 
24 
23 
28 
27 

22 

34 
34 
28 
24 
26 
26 
29 
31 
25 
31 
37 
36 

30 

21 
19 
24 
22 
23 
19 
24 
21 
21 
19 
18 
19 

21 

10 
11 
16 
16 
16 
15 
16 
13 
13 
10 
9 
11 

13 

5 
6 
8 
10 
10 
12 
8 
8 
10 
7 
5 
6 

8 

March            

April                                               

May       

JUly                                                                                                                                            

October  

Year                   •           

NORTH  PLATTE,  NEBR. 
(Elevation  above  sea,  2,809  feet;  anemometer  above  ground,  52  feet.) 


32 

42 

16 

6 

3 

1 

0 

31 

37 

17 

9 

4 

1 

1 

March             

26 

34 

21 

11 

5 

2 

1 

April                                                

20 

30 

22 

14 

7 

3 

4 

May  

19 

31 

26 

14 

6 

3 

1 

23 

34 

21 

12 

6 

3 

1 

JUly         

28 

35 

23 

10 

3 

1 

0 

81 

38 

20 

9 

2 

0 

0 

33 

33 

19 

10 

4 

1 

0 

34 

36 

17 

7 

3 

2 

1 

36 

36 

13 

8 

4 

2 

1 

37 

39 

14 

2 

1 

0 

Year 

29 

35 

19 

10 

4 

2 

1 

PUEBLO,  COLO. 

(Elevation  above  sea,  4,653  feet;  anemometer  above  ground,  81  feet.) 


CO 

25 

8 

4 

3 

1 

1 

February  ...  .        

48 

28 

g 

6 

5 

2 

2 

March                                                    •          

45 

29 

13 

7 

3 

2 

1 

April  

37 

32 

14 

8 

4 

3 

2 

Mav 

39 

31 

15 

g 

4 

2 

1 

43 

29 

17 

7 

3 

1 

0 

JUly                                   

43 

34 

16 

6 

1 

52 

31 

12 

4 

1 

52 

31 

13 

3 

1 

October                                                   

57 

28 

8 

4 

2 

1 

59 

24 

8 

4 

3 

1 

1 

December                

54 

25 

9 

5 

4 

2 

1 

Year  

49 

29 

12 

5 

3 

1 

1 

LANDER,  WYO. 
(Elevation  above  sea,  5,373  feet;  anemometer  above  ground,  34  feet.) 


so 

11 

4 

g 

1 

1 

1 

February   

84 

10 

4 

1 

1 

o 

o 

March                                                                  

75 

14 

6 

3 

1 

1 

o 

April  

65 

23 

g 

3 

1 

0 

o 

May  

67 

22 

8 

3 

0 

0 

o 

68 

19 

8 

4 

1 

July 

71 

18 

rv 

3 

1 

August                                 .              

79 

15 

4 

2 

71 

17 

7 

3 

1 

October  

84 

9 

4 

2 

1 

82 

10 

3 

2 

1 

1 

1 

80 

12 

4 

2 

1 

1 

15 

C 

.) 

1 

o 

o 

19 


TABLE  II. — Summary  of  wind  movement,  in  perce?itages— Continued. 

SALT  LAKE  CITY.  UTAH. 
{.Elevation  above  sea,  4,334  feet;  anemometer  above  ground,  90  feet,  i 


Miles  per  hour. 

0-5.      6-10. 

11-15.    16-20.    21-25.    26-30.    31+ 

January               ....                  

83 
73 
61 
56 
56 
55 
58 
63 
61 
72 
74 
72 

65 

11 
17 
25 
25 
27 
29 
29 
28 
27 
20 
16 
18 

23 

3 
6 
9 
13 
11 
12 
11 
7 
8 
6 
6 
6 

8 

1 

3 
4 
4 
3 
2 
2 
3 
2 
3 
3 

3 

1 
1 
2 
2 
2 
1 
0 
0 
1 
0 

1 

1 

1 

March 

\pril                                                                  

May 

Julv 

\U£TUSt   . 

October  

Year 

YUMA,  AEIZ. 
(Elevation  above  sea,  40  feet;  anemometer  above  ground,  50  feet.) 


54 

25 

13 

6 

2 

o 

52 

26 

11 

7 

3 

1 

March                                                 

49 

?? 

12 

8 

3 

1 

\nril 

47 

29 

12 

7 

3 

2 

Mav                                                   

43 

33 

14 

6 

3 

1 

47 

37 

13 

3 

o 

o 

JUly                                                                

42 

36 

16 

5 

1 

0 

45 

36 

16 

3 

o 

o 

September                .               

58 

31 

8 

2 

1 

o 

October 

65 

24 

8 

2 

1 

o 

November     

61 

25 

10 

3 

1 

o 

58 

24 

11 

6 

1 

o 

Year 

52 

29 

12 

5 

2 

o 

CO 


8 


I 


1 


. 


r 


UNIVERSITY  OF  CALIFORNIA  LIBRARY 
BERKELEY 


Return  to  desk  from  which  borrowed. 
This  book  is  DUE  on  the  last  date  stamped  below. 


12  1948 


JUM     41981 


JUI 


LD  21-100m-9,'47(A5702sl6)476 


I 


